From German published patent application DE-OS No. 3,130,380, an idle-speed control system is known wherein an increase in the engine speed desired value with a delayed fall-off is made to follow the increase in the actual engine speed value. Also, reference may be made to U.S. patent application Ser. No. 657,212 entitled "Apparatus for Influencing Control Quantities of an Internal Combustion Engine" which was filed on Oct. 3, 1984 and is assigned to the same assignee as the present application. This other application discloses a smooth-running control system wherein each cylinder of the engine has a control unit corresponding thereto. These two control systems now are to operate jointly to act on the amount of fuel metered to the individual cylinders. The simplest way to accomplish this would be to combine the output signals of the two control systems in a combining logic operation, where required, and form a suitable signal as described in the above-identified United States patent application.
In such a combining logic operation, both control systems would have equal access to the fuel metering apparatus. However, the smooth-running control system referred to above is in a position to dampen vibrations of the vehicle only if its output signal is delivered to the fuel metering apparatus as rapidly as possible to thereby act upon the quantity of fuel to be injected also as rapidly as possible. This can only be accomplished if the two control systems are not treated equally but, rather, if the smooth-running control system has priority status.